Effect of Malignancy Rates on Cost-effectiveness of Routine Gene Expression Classifier Testing for Indeterminate Thyroid Nodules

Background: The value of gene expression classifier (GEC) testing for cytologically indeterminate thyroid nodules lies in its negative predictive value, which is influenced by the prevalence of malignancy. We incorporated actual GEC test performance data from a tertiary referral center into a cost-effectiveness analysis of GEC testing.

Methods: We evaluated consecutive patients who underwent GEC testing for Bethesda category III and IV nodules from 2012 to 2014. Routine GEC testing was compared with conventional management by the use of a decision tree model. Additional model variables were determined via literature review. A cost-effectiveness threshold of $100,000 per quality-adjusted life-year (QALY) was used.

Results: The prevalence of malignancy was 24.3% (52/214). Sensitivity and specificity of GEC testing were 96% and 60%. Conventional management cost $11,119 and yielded 22.15 QALYs. Routine GEC testing was more effective and more costly, with an incremental cost-effectiveness ratio of $119,700/QALY, making it not cost-effective. At malignancy rates of 15, 25, or 35%, routine GEC testing became cost-effective when the cost of GEC testing fell below $3,167, $2,595, or $2,023.

Conclusion: The cost-effectiveness of routine GEC testing varies inversely with the underlying prevalence of malignancy in the tested population. The value of routine GEC testing should be assessed within the context of institution-specific malignancy rates.